Re: [PATCH v7 05/15] drm/imx: dc: Flag CRTC status in GERNERALPURPOSE register

[Laurentiu Palcu]

On Mon, Oct 26, 2026 at 06:05:10PM +0800, Liu Ying wrote:
> Map Display Controller's register GERNERALPURPOSE at offset 0x100 and
> create an MMIO regmap to access the register.  Create helpers
> dc_drv_flag_crtc_{enable,disable}() with the 2 LSB bits in the register
> to flag the CRTC enablement/disablement status.  Also, create a helper
> dc_drv_crtc_was_enabled() so that the CRTC driver can use it to check
> if the CRTC was enabled by a previous boot or not.  This is a preparation
> for an upcoming patch to disable display controller at boot if the CRTC
> was enabled by the driver during a previous boot instead of a bootloader.
> 
> Signed-off-by: Liu Ying <victor.liu@xxxxxxx>
> --
> v7:
> - Newly introduced in v7 as a preparation for fixing Sashiko AI bot's
>   comment on an upcoming patch.  (Sashiko AI bot)
> ---
>  drivers/gpu/drm/imx/dc/dc-drv.c | 76 +++++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/imx/dc/dc-drv.h |  7 ++++
>  2 files changed, 83 insertions(+)
> 
> diff --git a/drivers/gpu/drm/imx/dc/dc-drv.c b/drivers/gpu/drm/imx/dc/dc-drv.c
> index 13795a2ad735..ac1321adf1c8 100644
> --- a/drivers/gpu/drm/imx/dc/dc-drv.c
> +++ b/drivers/gpu/drm/imx/dc/dc-drv.c
> @@ -13,6 +13,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/pm.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/regmap.h>
>  
>  #include <drm/clients/drm_client_setup.h>
>  #include <drm/drm_atomic_helper.h>
> @@ -28,9 +29,21 @@
>  #include "dc-drv.h"
>  #include "dc-pe.h"
>  
> +/* General Purpose register offset used to flag driver usage. */
> +#define GENERALPURPOSE		0x100
> +#define  CRTC_ENABLED(x)	BIT(x)
> +
>  struct dc_priv {
>  	struct drm_device *drm;
>  	struct clk *clk_cfg;
> +	struct regmap *gp_regmap;
> +};
> +
> +static const struct regmap_config dc_gp_regmap_config = {
> +	.reg_bits = 32,
> +	.reg_stride = 4,
> +	.val_bits = 32,
> +	.max_register = 0,
>  };
>  
>  DEFINE_DRM_GEM_DMA_FOPS(dc_drm_driver_fops);
> @@ -156,6 +169,8 @@ static int dc_probe(struct platform_device *pdev)
>  {
>  	struct component_match *match = NULL;
>  	struct dc_priv *priv;
> +	struct resource *r;
> +	void __iomem *base;
>  	int ret;
>  
>  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> @@ -167,6 +182,28 @@ static int dc_probe(struct platform_device *pdev)
>  		return dev_err_probe(&pdev->dev, PTR_ERR(priv->clk_cfg),
>  				     "failed to get cfg clock\n");
>  
> +	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!r)
> +		return -EINVAL;
> +
> +	if (!devm_request_mem_region(&pdev->dev, r->start + GENERALPURPOSE, 4,
> +				     dev_name(&pdev->dev))) {
> +		dev_err(&pdev->dev, "failed to request memory region\n");
> +		return -EBUSY;

Use 'return dev_err_probe()'.

> +	}
> +
> +	base = devm_ioremap(&pdev->dev, r->start + GENERALPURPOSE, 4);
> +	if (!base) {
> +		dev_err(&pdev->dev, "failed to do ioremap\n");
> +		return -ENOMEM;

Use 'return dev_err_probe()'.

> +	}
> +
> +	priv->gp_regmap = devm_regmap_init_mmio(&pdev->dev, base,
> +						&dc_gp_regmap_config);
> +	if (IS_ERR(priv->gp_regmap))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(priv->gp_regmap),
> +				     "failed to init General Purpose regmap\n");
> +
>  	dev_set_drvdata(&pdev->dev, priv);
>  
>  	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> @@ -196,6 +233,45 @@ static void dc_remove(struct platform_device *pdev)
>  	component_master_del(&pdev->dev, &dc_drm_ops);
>  }
>  
> +void dc_drv_set_crtc_enable(struct dc_drm_device *dc_drm,
> +			    unsigned int crtc_index)
> +{
> +	struct dc_priv *priv = dev_get_drvdata(dc_drm->base.dev);
> +
> +	if (WARN_ON(crtc_index > 1))
> +		return;
> +
> +	regmap_set_bits(priv->gp_regmap, 0, CRTC_ENABLED(crtc_index));
> +}
> +
> +void dc_drv_set_crtc_disable(struct dc_drm_device *dc_drm,
> +			     unsigned int crtc_index)
> +{
> +	struct dc_priv *priv = dev_get_drvdata(dc_drm->base.dev);
> +
> +	if (WARN_ON(crtc_index > 1))
> +		return;
> +
> +	regmap_clear_bits(priv->gp_regmap, 0, CRTC_ENABLED(crtc_index));
> +}
> +
> +bool dc_drv_crtc_was_enabled(struct dc_drm_device *dc_drm,

I believe it would be better to rename this one to 'dc_drv_crtc_is_enabled'.
After all, you're checking whether the crtc is enabled *now*. Reading those
bits in GENERALPURPOSE show the current status, not a past one.

With the above addressed:
Reviewed-by: Laurentiu Palcu <laurentiu.palcu@xxxxxxxxxxx>

-- 
Thanks,
Laurentiu